Research On Non-explosive Underwater Shock Loading Technique And Blast Resistant Properties Of Aluminium Alloy Structures

The underwater explosion shock wave and bubble pulsating are the main influencing factors of the fatal damage of warships structure in the non-contact explosion case. The study about the performance of anti-explosion and anti-shock for naval ships under underwater explosion become a concern of countries with the strong naval power. Experimental methods supported by the reliable data showed superior to other reported techniques. The experiments of strong underwater shock loading on naval ships are of great importance for the development of anti-shock performance in naval ships. The requirement of a light maritime combat force is becoming strong with the disputes arising over maritime territory. The design of lightweight naval ships with the improvement of anti-shock performance is becoming a new study hotspot for the world-wide researchers. Based on the backgrounds and reasons above, the lab-scale technology of shock wave loading and the damage mechanism and the protective performance of light-weight structures under the condition of underwater explosion shock loading were investigated in the present study, through the experimental combination of theory and numerical simulation. The main studies were as follows: The reliability of the lab-scale device providing underwater explosion shock wavewas verified by the experiments of non-explosive underwater explosion shock wave loading and numerical simulations. The influencing factors of shock wave strength and decay constant on the flyer mass, impact velocity of flyer and piston mass were investigated. Then the expression of peak of shock wave and decay constant was established based on the simulation and experimental results. The real-time dynamic deformation histories of clamped aluminum alloy circularplates were obtained by using a digital high-speed camera under the condition of low intensity underwater explosive shock loading. The mechanical model of real-time dynamic strain field of the plate was built according to the principle of employing the same volume and rigid-plastic assumption. Then the quasi-static tensile mechanical experiments of5A06aluminum alloy were conducted by the universal testing machine at the temperatures ranging from room temperature to300oC. The dynamic tensile mechanical experiments of5A06aluminum alloy were carried out with the SHTB bars at the high strain rates. Based on the obtained experimental results, a modified Johnson-Cook constitutive relation was built by changing the softening effect condition, and the validation of the J-C constitutive relation was verified by the underwater shock loading tests and corresponding simulations. Finally, the formation and collapse of bubbles caused by fluid-structure coupling were obtained under the conditions of non-explosive underwater explosion shock wave loading, and the dynamic responding characteristics of target plate were investigated by using numerical simulations.The expression of strength and decay constant of underwater shock wave of high intensity were obtained by using a cylindrical loading devices for non-explosive underwater shock. The whole physical process of typical failure modes of clamped air-back circular plates was observed by high-speed photography based on the experiments of non-explosive underwater shock loading with high intensity. The real-time measurements for dynamic deformation of target plates were carried out through the3D digital speckle correlation method (DIC). Based on the decoupling fluid-structure interaction, the critical conditions of different failure modes were obtained by corresponding simulations in the scope of the present experimental results.Compared with the experimental results of monolithic panels of equivalent area mass, the effects of three sandwich panel structures with different cores on anti-shock performance were studied by the experiments of underwater shock loading and corresponding simulations. The relationship between the most deflects of air-back plate of sandwich panels and non-dimensional impulse of underwater shock wave was obtained, and the anti-shock performances of three kinds of sandwich structure were determined.The findings of this present study, which have the certain reference and guiding values in practice, might provide the essential experimental data and theoretical basis for the experimental study of anti-shock performance and lightweight design of naval ship structure in the condition of underwater explosion shock loading in laboratory.